Temperature responsive device



June 23, 1942. F, D JOESTING I 2,287,177

TEMPERATURE RESPONS IVE DEVICE Filed Sept. 1, 1939 inventor .Ergaerick, D. {Toasting Patented June 23, 1942 TEMPERATURE RESPONSIVE DEVICE Frederick D. Joesting; Chicago, Ill., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application September 1. 1939, Serial No. 293,091

4 Claims.

This invention is directed broadly to a temperature sensitive device and more particularly to a ribbon type of device which is adaptedto respond to radiant heat. The amount of work which can be derived from an expansible metal ribbon depends to a great extent upon the manner in which biasing forcesare applied to it. If the ribbon is under an initial tension when it is cold and no biasing forces are applied, then the expansion due to an increase in temperature will go chiefly to relieving the tension and substantially no work will be accomplished by the ribbon.

One of themain objects of this invention is to bias the ribbon for bending in one direction upon expansion thereby placing it under an initial tension, and to automatically maintain that tension constant for all temperatures whereby the maximum amount of work may be obtained from the ribbon- Another object is to actuate a motion multiplying lever by the ribbon so that the relatively small movement of the ribbon may be considerably amplified in order to perform the desired work.

Still another object is to make the ribbon in the form of an elongated strip of expansible metal, to mount the ends of the strip over rounded surfaces of a pair of bearing members,

and to split the ends of the strip longitudinally to relieve any stresses in the strip due to assembly or to expansion of the strip crosswise. A further object is to clamp the ends of the strip to a support by these same bearing members.

These and other objects will readily become apparent as the following specification is read in the light of the accompanying drawing in which Figure 1 is an elevational view looking at the i back of the supporting member, the biasing spring being removed,

Figure 2 is a section taken along the line 2-2 of Figure 1 with the biasing spring in place, and

Figure 3 is a detail view of the ribbon mounting showing one of the split ends.

Referring to Figures 1 and 2 of the drawing,

'ihe reference numeral H indicates generally a These brackthe rounded portions l6 of the brackets and-these ends reverse upon themselves and extend between the brackets l and the face l2 of the supporting member. A series of screws l8 are screw threaded through the face l2 of the supporting member, the ribbon I1, and the supporting brackets l5 thereby securely clamping the ends to the ribbon l'l between the face [2 of the supporting member and the inner face of the brackets IS. The brackets l5 extend transversely of the ribbon H and are of the same, width as the ribbon so that the ribbon is carried snugly and evenly by the brackets. stress which may beset up. in the ends of the ribbon when they are clamped in position by the brackets l5 and screws 18, they are slit as shown at in Figure 3. By slitting the'ends of the ribbon any tendency of the ribbon to wrinkle is reduced.

An additional function of these slits is to reduce stress in the ribbon due to crosswise expan-' sion. The ribbon and support being of different materials will expand differently on changes in temperature and these slits break up the distance andreduce the amount of sliding between the ribbon and support on expansion.

The ribbon ll is provided with a center verti cal slot 2| as shown in Figure 2 through which is inserted one end 22 of a connecting link 23. An elongated U shaped bearing member 24 extends transversely of the ribbon at its mid portion and the rounded bottom of the U bears against the ribbon. This bearing member 24 is provided with a slot at its mid portion as indicated in dotted lines at 25. The end 22 of the link 23 is provided with anopening 26 which is adapted to receive the bearing member 24 and the edge 21 of the opening 26 is inserted in the slot in the bear- I ing memberto prevent it from moving laterally.

Lateral movement of the link 23 is prevented byv the sides of the slot 2|.

means such as the rivets 32. g the U shaped bracket -3I carry an. axle..33-;;cn

. which is pivotally mounted a lever 34. Thlsilcvcr;

is provided with a hole through which the 1 other end 36 of the link 23 is inserted. This end of the link carries a cross pin 31 which rides in a depression in the lever 34 so that when the,

lever 34 rotates in a clockwise direction it pulls the link 23 with it.

ets IS. The ends of this ribbon are supported by The upper portion *of the supportingvmember In order to relieve any u is provided with a downwardly extending m 40 in which is hooked one end 4| of a tension spring 42. The other end 43 of this spring is looped through a hole 44, in the lever34, this hole being on the opposite side of the axle 33 from the ear 40. The portion 45 of the lever 34 which is farthest from the axle 33 is adapted to operate a switch actuating member of any desired form.

The above described device is intended to be mounted in some such manner as the device dis-. closed in the copending application to Daniel G. Taylor Serial No.284,007 filed July 12, 1939, so that the ribbon ll looks directly into the combustion chamber of a furnace. to respond to the radiant heat of combustion and the surface is therefore blackened in orderthat it may more readily absorb such radiant heat.

The ribbon I1 is portion of the ribbon i1. so that the switch actuating rod which is connected to the lever 34.at 45 may have a greater motion per degree temperature change than the ribbon ll.

As certain changes and modifications of this devlcewill occur to those who are skilled in the art I wish it to be understood that I "m to be limited only by the scopeof the appended claims and not by the specific embodiment disclosed.

I claim as my invention:

1. A temperature responsive device comprising in combination, a relatively non-expansible support, a relatively expansible elongated one-piece metal ribbon, and a pair of mounting members having rounded surfaces over which theends of said metal ribbon are stretched, said ends being split to relieve internal stresses which may be set up in them due to mounting or dimensional variations due to temperature changes.

2. A temperature responsive device comprising incombination, a relatively nofi-expansible support. a relatively expansible elongated one-piece metal ribbon, a pair of clamps mounted on said support and having oppositely directed rounded 23 toward-the left bending the ribbon. As the lever 34 is'rotated in a clockwise direction the angle between this lever and the spring 42 is increased, thereby increasing the rotative effect which this spring has upon the lever. The result is that the more the ribbon ll expands the greater will be. the force exerted thereon by the link 23. The spring and lever are arranged in this manner so that the tension of the ribbon II will remain substantiallythe same at all temperatures. It'will be appreciated that'when the ribbon I1 is nearly straight a relatively small force exerted thereon by the link 23 is sufficient to produce a predetermined initial tension but that as the ribbon expands and bows la much larger force is required to maintain that same tension dueto the different angular relationship between the link 23 and the ribbon I1. I

. If the same tension were not maintained in the ribbon for all temperatures, the device would not operate at its greatest efficiency. For example,

if the ribbon H were under a predetermined ini-' tial" tension and the temperature caused the ribbon toexpand, the immediate effect would be to reduce the tension on the ribbon due to the ex-;

pansion which'in turn'jwould reduce the amount of work which the ribbon was capable of doing. I

In other words, part of the' ribbon expansion would be taken up in relieving the tension on the ribbon instead of in doing useful work. By my novel arrangement of the spring and lever, however, the tension on the ribbon remains substantially the same so that all of the expansion is used to perform useful work.

When combustion within the furnace ceases to exist and ,.-the ribbon I'I cools, it contracts and straightens which reduces the angle between the sprin g fl and the lever 34 and the parts return tothe position shown in Figure 2.- n

, Another advantage of the present device is that the lever 34 amplifies the motion of the central surfaces, the ends of said metal ribbon extending over said rounded surfaces and reversing in direction to extend between said clamps and said support, and screw means cooperating with said clamps for tightening them against said support to securely hold the ends of said metal ribbon, V

lever from said support, said spring exerting a rotative force on said lever which places said ribbon under an initial tension, expansion of said ribbon due to a rise in temperature permitting saidspring to rotate said lever in a direction to increase the anglebetween said lever and said spring, said angle being of such size that as the angle is increased upon expansion of said ribbon the increased rotative force exerted by said spring on said lever is sufficient to maintain said ribbon under a substantially constant tension.

4. A temperature responsive device comprising in combination, an expansible ribbon, a pivoted lever operatively connected at an intermediate portion thereof with a movable portion of said ribbon, means exerting a substantially constant force on the free end of said lever at an acute angle with respect to said lever whereby said ribbon is placed under tension and biased for movement in one direction upon expansion thereof,

f lever arm of said lever, and hence the, force exerted thereby on said ribbon, sufficiently rapidly to maintain said ribbon under a substantially constant tension.

FRED-ERICK n. JOESTING. 

